Titanium base alloys



United States Patent TITANIUM BASE ALLOYS Application September 13, 1952, Serial No. 309,554

4 Claims. (Cl. 75175.5)

No Drawing.

This invention relates to alloys and, in particular, to titanium base alloys.

An object of this invention is to produce a titanium base alloy suitable for use at elevated temperatures of 400 F. to 800 F.

Another object of this invention is to provide a titanium base alloy having a mixture of the alpha and beta phases of titanium and in which the beta phase is stable when the alloy is subjected in use to a temperature within the range of 400 F. to 800 F.

A further object of this invention is to provide a titanium base alloy containing iron, chromium, molybdenum and aluminum.

A more specific object of this invention is to provide an alloy consisting of 1% to 4% iron, 1% to 4% chromium, 1% to 4% molybdenum, 1% to 6% aluminum and the balance titanium with incidental impurities.

Other objects of this invention will become apparent from the following description.

In accordance with this invention the alloy comprises iron, chromium, molybdenum and aluminum alloyed in a titanium base in proper proportions to obtain an alloy having good mechanical properties and which is stable when used at operating temperatures of 400 F. to 800 F. In practice, the components are present in the alloy within the range of 1% to 4% iron, 1% to 4% chromium, 1% to 4% molybdenum, and 1% to 6% aluminum and the balance titanium with not over 0.5% of incidental impurities such as oxygen, nitrogen and carbon. Preferably the impurities are not present in amounts of more than 0.2% of any one of oxygen, nitrogen and carbon. In practice, it has been found desirable to maintain the elements iron, chromium and molybdenum in substantially equal amounts in the alloy of this invention as Will be evident from the results given hereinafter.

While the alloying elements utilized in the alloy of this invention are employed in fairly specific ranges as given hereinbefore, the preferred composition range withice incidental impurities not exceeding 0.5%. Such alloys are found to have especially good mechanical properties.

The alloy is preferably made from commercially pure titanium, that is the titanium metal commercially available such as is produced from the reaction of chemically pure titanium tetrachloride with magnesium metal and containing not more than 0.25% oxygen, 0.15% nitrogen, and 0.10% carbon present as impurities. In practice the titanium is preferably melted by the electric arc process in a water-cooled copper crucible in an atmosphere such as argon or helium which is non-contaminating to titanium, the alloying elements being added to the melt either as chemically pure components, or where desired, the iron, chromium and molybdenum is added in the form of high purity ferro-alloys of chromium and molybdenum.

The alloy thus formed having the components within the ranges given hereinbefore is found to consist of a mixture of the alpha, low temperature, hexagonal closepacked phase and the beta, high temperature, body-centered cubic crystal structure phase, which mixture is retained over a wide range of temperature. From the results obtained with the alloys of this invention it is believed that the elements iron, chromium and molybdenum within the ranges given tend to go into solution and to stabilize the beta phase Whereas the aluminum content tends to stabilize and strengthen the alpha phase. All of the alloying components when present in the ranges given have the effect of increasing the strength of the resulting base alloy when such alloy is subjected in use to temperatures of 400 F. to 800 F. The elements iron, chromium and molybdenum are of particular value in the ranges given of functioning to provide a stable beta phase which will not decompose and embrittle the alloy during long service at elevated temperatures in the range of 400 F. to 800 F.

The alloys produced as described can be readily forged or rolled to sheet, bar or other form from a temperature of 1300 F. to 1800 F. Thereafter they are annealed at a temperature of 1075 F. to 1200 F. and preferably at about 1100 F. for a period of time of up to twentyfour hours to effectively produce a mixture of the alpha and beta phases, the beta phase being completely stable when subjected to reheating as in service at a temperature in the range of 400 F. to 800 F.

As examples of the outstanding mechanical properties of alloys having the composition within the range given hereinbefore, reference may be had to the following table of results obtained on alloys produced and which were forged from a temperature of 1650 F. and then annealed for twenty-four hours at the temperature indicated.

001111305111, Percent Ingot Anneal. Tensile Elong., Red. in Heat No. Hardness, Temp., p S i Percent Area,

Fe Cr M0 A1 Bnnell F. 1 in. Percent K 900- 1. 3 1.4 1. 3 1. 0 280 1,200 126,500 25 56 K 901 1. 3 1. 4 1. 3 3. 0 321 1,200 180, 000 11 29.6 K 902--. 1. 3 1. 4 1. 3 5. 0 330 1,200 156, 000 18 46. 4 K 899--- 2.0 2.1 1. 9 1.0 317 1, 200 141,000 22 44. s K 807.-. 2. 0 2.1 1. 9 3. 0 370 1,200 153,000 20 42. 2 K s37-- 2. 0 2.1 1. 9 4. 0 375 1,100 179,000 19 51 K 808 2.0 2.1 1.9 5. 0 415 1, 200 190, 500 7 11 K 903 2. 7 2.8 2. 5 1. 0 291 1, 200 159, 000 22 41 K 483..... 2. 7 2. 8 2. 5 2. 0 330 1, 200 147, 700 22 48 K 838---" 2. 7 2.8 2. 5 4. o 351 1,100 191, 500 14 28 in the range given is one in which the elements are pres- As examples of other alloys produced within the range ent 1n the proportions of 1.2% to 2.7% 1ron, 1.3% to given and the exceptional mechanical properties which 2.8% chromium, 1.1% to 2.5% molybdenum, and 3% to 5% aluminum with the balance titanium with the can be obtained thereon, reference may be had to the following table, each of the alloys listed having been subjected to an annealing treatment at 1100 F. for twentyfour hours after forging.

Composition, Per- 0 27 Heat cent Tensile fi Elong., Red.

. St., p Percent in Area, No A St p s. 1. r 1 1n. Percent Fe Or Mo Al K 991. 1. 3 1. 4 1. 3 3.0 140, 500 140, 500 22 50 K 992 1. 3 l. 4 1.3 4. 0 151, 000 148, 800 16 45 K 993 1. 3 1. 4 1. 3 5. 0 165.000 164, 000 14 17 K 994.. 2.0 2.1 1. 9 3.0 143, 000 138, 500 19 43 K 995.-- 2.0 2. 1 1.9 5. 0 167, 500 167, 500 16 47 The mechanical properties of alloys K991 and K995 having the same composition as alloy K901 and K808,

I Elong. Red. in o Tensile Test Temp., F. St S L Pericgnt 1 Areghlger by any one skilled in the art and have excellent high temperature strength. This characteristic renders the alloy outstanding for use in jet engines where temperatures in the range of 400 F. to 800 F. are encountered in service. The fact that the beta phase will not decompose and cmbrittle when the alloy is used at elevated temperatures makes it possible to clearly prolong the life of components formed from the alloy for use at such elevated temperatures thereby greatly increasing the life of jet engines or other apparatus requiring the characteristic of long service at elevated temperatures.

1 claim:

1. An alloy consisting of,'1% to 4% iron, 1% to 4% chromium, 1% to 4% molybdenum, 1% to 6% aluminum and the balance titanium with incidental impurities.

2. An alloy consisting of, iron, chromium and molyb-v V Y impurities. I

balance titanium with incidental impurities and which has been annealed at a temperature of 1075 F. to 1200 F.

No references cited. 

1. AN ALLOY CONSISTING OF, 1% TO 4% IRON, 1% TO 4% CHROMIUM, 1% TO 4% MOLYBDENUM, 1% TO 6% ALUMINUM AND THE BALANCE TITANIUM WITH INCIDENTAL IMPURITIES. 